Trends and Challenges in the Operation Of Pumped-

Storage Hydro-power Plants

Dr Kwang Y Lee

Introduction

Pumped hydro storage

bull Pure off-stream PHS - which rely entirely on water that were previously pumped into an upper reservoir as the source of energy ndash also referred to as closed loop system

bull Combined PHS - which use both pumped water and natural stream flow water to generate power

bull Turbine to grid efficiency ndash 50 to 80 (GE proposes gt95)bull Earliest operation in 1890 in Switzerland with separate pump impeller and

propeller turbinebull The arrival of single pump-turbine in 1950rsquos changed the market for PHSbull Rapid growth in PHS market can be mainly attributed to the increased

penetration of intermittent renewable energy resourcesbull Most recent advances include

ndash Variable speed PHSndash Sea water PHSndash Compressed air PHSndash Under-sea PHS

Barriers to PHS and overcoming them

bull High investment costs (around 536 to 2474 $kW) and the difficulty to recover this cost

bull Factors affecting recovery of investment costndash Income from price arbitrage between peak and off-peak hours is

enough in just a few electricity markets ndash PSHPs are obliged to pay grid fees for the usage of transmission

lines when they are consuming as it occurs in many power systems such as the Spanish system or

ndash high water fees for utilizing rivers or lakes reduce profits of PSHP operation

bull Hence the operation in only peak-shaving based markets is not profitable However many research in the literature have displayed the operation of the PHS plant to be more profitable in the secondary regulation market

Advantages of PHS

bull Regulatory and reserve power - can participate in various reserves and regulatory actions of the market

bull Provides the highest power and energy density

bull Quick start and Black start capability

bull High ramp rate and instant voltage and frequency support capability

bull High round-trip efficiency gt80

[1]

bull Technical maturitybull Significant remaining potential

Image Courtesy - NREL

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Introduction

Pumped hydro storage

bull Pure off-stream PHS - which rely entirely on water that were previously pumped into an upper reservoir as the source of energy ndash also referred to as closed loop system

bull Combined PHS - which use both pumped water and natural stream flow water to generate power

bull Turbine to grid efficiency ndash 50 to 80 (GE proposes gt95)bull Earliest operation in 1890 in Switzerland with separate pump impeller and

propeller turbinebull The arrival of single pump-turbine in 1950rsquos changed the market for PHSbull Rapid growth in PHS market can be mainly attributed to the increased

penetration of intermittent renewable energy resourcesbull Most recent advances include

ndash Variable speed PHSndash Sea water PHSndash Compressed air PHSndash Under-sea PHS

Barriers to PHS and overcoming them

bull High investment costs (around 536 to 2474 $kW) and the difficulty to recover this cost

bull Factors affecting recovery of investment costndash Income from price arbitrage between peak and off-peak hours is

enough in just a few electricity markets ndash PSHPs are obliged to pay grid fees for the usage of transmission

lines when they are consuming as it occurs in many power systems such as the Spanish system or

ndash high water fees for utilizing rivers or lakes reduce profits of PSHP operation

bull Hence the operation in only peak-shaving based markets is not profitable However many research in the literature have displayed the operation of the PHS plant to be more profitable in the secondary regulation market

Advantages of PHS

bull Regulatory and reserve power - can participate in various reserves and regulatory actions of the market

bull Provides the highest power and energy density

bull Quick start and Black start capability

bull High ramp rate and instant voltage and frequency support capability

bull High round-trip efficiency gt80

[1]

bull Technical maturitybull Significant remaining potential

Image Courtesy - NREL

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Pumped hydro storage

bull Pure off-stream PHS - which rely entirely on water that were previously pumped into an upper reservoir as the source of energy ndash also referred to as closed loop system

bull Combined PHS - which use both pumped water and natural stream flow water to generate power

bull Turbine to grid efficiency ndash 50 to 80 (GE proposes gt95)bull Earliest operation in 1890 in Switzerland with separate pump impeller and

propeller turbinebull The arrival of single pump-turbine in 1950rsquos changed the market for PHSbull Rapid growth in PHS market can be mainly attributed to the increased

penetration of intermittent renewable energy resourcesbull Most recent advances include

ndash Variable speed PHSndash Sea water PHSndash Compressed air PHSndash Under-sea PHS

Barriers to PHS and overcoming them

bull High investment costs (around 536 to 2474 $kW) and the difficulty to recover this cost

bull Factors affecting recovery of investment costndash Income from price arbitrage between peak and off-peak hours is

enough in just a few electricity markets ndash PSHPs are obliged to pay grid fees for the usage of transmission

lines when they are consuming as it occurs in many power systems such as the Spanish system or

ndash high water fees for utilizing rivers or lakes reduce profits of PSHP operation

bull Hence the operation in only peak-shaving based markets is not profitable However many research in the literature have displayed the operation of the PHS plant to be more profitable in the secondary regulation market

Advantages of PHS

bull Regulatory and reserve power - can participate in various reserves and regulatory actions of the market

bull Provides the highest power and energy density

bull Quick start and Black start capability

bull High ramp rate and instant voltage and frequency support capability

bull High round-trip efficiency gt80

[1]

bull Technical maturitybull Significant remaining potential

Image Courtesy - NREL

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Barriers to PHS and overcoming them

bull High investment costs (around 536 to 2474 $kW) and the difficulty to recover this cost

bull Factors affecting recovery of investment costndash Income from price arbitrage between peak and off-peak hours is

enough in just a few electricity markets ndash PSHPs are obliged to pay grid fees for the usage of transmission

lines when they are consuming as it occurs in many power systems such as the Spanish system or

ndash high water fees for utilizing rivers or lakes reduce profits of PSHP operation

bull Hence the operation in only peak-shaving based markets is not profitable However many research in the literature have displayed the operation of the PHS plant to be more profitable in the secondary regulation market

Advantages of PHS

bull Regulatory and reserve power - can participate in various reserves and regulatory actions of the market

bull Provides the highest power and energy density

bull Quick start and Black start capability

bull High ramp rate and instant voltage and frequency support capability

bull High round-trip efficiency gt80

[1]

bull Technical maturitybull Significant remaining potential

Image Courtesy - NREL

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Advantages of PHS

bull Regulatory and reserve power - can participate in various reserves and regulatory actions of the market

bull Provides the highest power and energy density

bull Quick start and Black start capability

bull High ramp rate and instant voltage and frequency support capability

bull High round-trip efficiency gt80

[1]

bull Technical maturitybull Significant remaining potential

Image Courtesy - NREL

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Image Courtesy - NREL

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Peak shaving mode

Image courtesy - Wikipedia

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Profitability and bidding

bull Bidding strategy 1- peak shaving

bull Bidding strategy 2- ancillary services

bull Bidding strategy 3- biding simultaneously in both can almost double the profitability ndash requires heuristic optimization

Current market trends

bull Generating on week days and pumping on weekends have proved to be more profitable - They generate more on weekdays and pump more during weekends

bull Within a season generation and pumping schedules do not change much - Both generating and pumping hours are twice as much in winter than in summer

Current Challenges

bull Considering the uncertainty of real time use of regulation reserves

bull Revising the methods used to determine long term guidelines

bull Defining the optimal strategy for PSHPs with variable speed and hydraulic short-circuit operation

bull Modeling and design of hydraulic short circuit and variable speed machines and equipments and their grid connected advantages

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Modern trends in pumped hydro

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Evolution of Pumped Hydro

Separate pump and turbine

bull Two hydraulic machines

bull Two different shafts

bull Two electrical machines

Reversible pump turbine

bull One hydraulic machine

bull One shaft

bull One electric machine

Ternary set

bull Two hydraulic machines but same shaft

bull One electric machine

bull One shaft

bull Voithbull Seimensbull GE

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Variable speed pumped hydro -Benefits

bull Benefits of variable speed operation

ndash Variable speed could help avoid draft tube pressure oscillations and cavitation among others

ndash Improved performance at off-design heads and improved range of heads

ndash Improved performance at off-design discharge and improved range of discharge

ndash Variable speed allows power consumed in the pumping mode to be varied over a range of outputs

ndash Variable speed also allows the turbine to operate the turbine at peak efficiencies over a wide range of its operating band

ndash Doubly fed induction generators fed through thyristor cyclo-converters are extremely beneficial for grid connected operations

Speed discharge characteristics of a turbine [2]

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Variable speed operation - Control

bull 2 important methods similar to wind are ndash Pitch control ndash high flow rate ndash comparatively

small time constant

ndash Load control ndash medium flow rate ndash slow due to the large inertia involved

These equations are used to control the turbine gate angle and the speed so as

to obtain power output set-point under any particular head (fortunately they are

linear)

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Variable Speed operation ndash Electrical machine

bull Static frequency converters have been used before but for smaller purposes (lt30 MVA) but for ratings above 250 MVA this solution becomes infeasible Thus the use of DFIM sets into the picture The converter needed for the DFIM depends directly upon the slip for which it is optimized to operate

bull The wound rotor induction machine has come up from the wind turbine industry Control of DFIM is possible through rotor and stator side converters

bull ldquoVARSPEEDrdquo by ABB is one famous commercial example advantages of which arendash Increased overall efficiencyndash Possibility of active power control in pumping mode ndash Possibility of reactive power control at interconnection point to the grid

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Variable speed operation - DFIM

bull DFIM is advantageous over the synchronous machine as itrsquos speed stabilizes faster than a conventional synchronous machine for a grid side voltage drop event Excellent self-stabilizing properties

bull The machine can be used to instantaneously inject real power into the grid The reduction in reference speed can be used to extract the required real power Conventional plants need accumulated steam for the same Thus they can be used for grid control

bull Due to the possibility of speed adjustment the pump power may easily be adjusted This feature is also advantageous for grid control Variable speed pumping

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Modern hydraulic equipment - Ternary Set

Pelton turbine Clutch and gear(torque coupler)

Multi-stage centrifugal pump

Tail-raceOutlet of pump

Turbine inlet scroll

Pumped storage hydraulic equipment with pump and turbine as separate hydraulic machines but on

the same shaft [3]

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Ternary Set

bull Using two separate hydraulic devices the direction of rotation will be the same in both modes of operation This is very convenient as far as uniform stress on the structure and electrical control and connections are concerned

bull The change-over time required between pumping and generating mode can be reduced due to the pre-rotating single ndash shaft Thereby enabling faster controls and no additional starting power requirements

bull Two modes are separated by a clutch which can engage either mode in no time

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Hydraulic short-circuit

bull In a ternary set it is possible to transfer the water from the pump to the turbine and drive the turbine and feed the upper reservoir simultaneously It may also be possible to supplement the flow of water into the turbine and hence reduce the discharge from the upper reservoir In both cases the ternary set acts as a controllable load

bull Direct shaft control is better and faster than generator control due to the large generator inertia Hence hydraulic short circuit enables the operation of a fixed load on the same shaft The difference between the pump power and the turbine power is only fed to the grid

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Hydraulic short-circuit

Valve control

Right now there is only one early access paper in IEEE and two papers in science direct that realize hydraulic short-circuit

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Wind Hydro a Unit Commitment Point of View for Co-ordination

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Hydraulic Constraints in operation of a PHS

Other than electrical constraints there are numerous hydraulic constraints which need to be considered

bull Energy content of a reservoirbull Mode of reservoir

ndash Pumpinggeneratingndash Different for units with ternary set ndash clutch setting constraint

bull Reservoir volume constraint different for upward and downward reservoir bull Unit ramp rate constraintbull Rate of change of discharge limitsbull Reservoir spill limitsbull Branch flow limits

With the introduction of the use of ternary sets and variable speed machines new and modified constraints will arise These are areas of research which need attention

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Wind hydro Operation ndash I ndash (research based)

bull [4] presents the operation of an under construction Greek island power system with a hybrid power sources consisting of a pumped storage station where pumping is facilitated by a wind farm Wind power dispatch methods -ndash Only for pumpingndash Penetration into the grid with a margin with wind curtailmentndash Direct dispatch to connected grid with the pumped storage

plant as a fast controller

bull Advantagesndash Increased RES penetration under the dispatch strategy as tested

under dry avg and wet hydrological years for both high and low wind profiles

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Wind hydro Operation ndash II ndash (research based)

bull Khodayar et al [5] presents the SCUC for a 6 bus power system where wind farm and PHS are at the same bus including thermal generators on other busses Here the PHS acted as a volatility controller for the wind farm With the co-ordination the following were realizedndash Reduction in curtailed number of units and hence

increase in wind penetration which proves the fast control ability of PHS

ndash Reduction in operation cost of other plants due to high RES penetration

ndash Increase in transmission network security

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Wind hydro Operation ndash III ndash (research based)

bull Khodayar et al [6] extended their work on SCUC to considering different scenarios with uncertainties such asndash Line generator or other equipment failure

ndash Forecast error

bull Monte-carlo simulations were used generate almost 3000 scenarios and scenario reduction techniques were used to consider 12 scenarios The scenarios were implemented under 4 different co-ordination strategiesndash Wind only along with other generation units

ndash Wind and hydro co-ordination with constant temporal pond level constraint

ndash Wind and hydro co-ordination with constant temporal power level constraint

ndash System level co-ordination with PHS dispatch optimized with the system

bull Criterion for selecting the best strategyndash Availability of units for control and regulation

ndash Corrective action cost ndash cost for performing actions apart from base case

ndash Total operation cost

ndash Wind curtailment

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Coordinated output and corrective output actions

Corrective action performed by

thermal plants is reduced due to

system level coordination of

PHS

Coordinated power output

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Pond level control Strategy ndash Inflexible to Grid and Wind Fluctuations

Pond level control

Constant power level

System level co-ordination

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Congestion and operation cost reduction strategy ndash system level coordination

Gen 3 is costly and is not committed when

strategy 4 is used Congestion is reduced

and so is operation cost

Wind only with other thermal units

Wind and PS coordinated at system level

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Challenges in retrofitting existing plants with modern

equipment of PHS

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Hydraulic design[7]

bull Hydraulic transients considering the existing waterways

bull Integration of new hydraulic components

bull Cavitation free operation with available runner settings

Electrical Design[7]

bull Synchronous generator with full power frequency converter

bull Replacing the Synchronous gen by a DFIM with low power frequency converter

Power Electronic control[7]

bull Harmonic filters

bull Voltage source inverter and transformer

bull Low frequency current and voltage transformers

bull Rotor feed equipment

Challenges in Reconfiguring an existing plant

Building a new one takes 8 years and millions

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo

Reference

bull [1] - Comparative Review of Long-Term Energy Storage Technologies for Renewable Energy Systems A Andrijanovits H Hoimoja D Vinnikov Department of Electrical Drives and Power Electronics Tallinn University of Technology

bull [2] - J Fraile-Ardanuy J R Wilhelmi J J Fraile-Mora and J I Perez Variable-speed hydro generation operational aspects and control in IEEE Transactions on Energy Conversion vol 21 no 2 pp 569-574 June 2006

bull [3] - httpvoithcomen11_06_Broschuere-Pumped-storage_einzelnpdf

bull [4] - Stefanos V Papaefthymiou Eleni G Karamanou Stavros A Papathanassiou Michael P Papadopoulos ldquoA Wind-Hydro-Pumped Storage Station Leading to High RES Penetration in the Autonomous Island System of Ikariardquo ieee TRANSACTIONS ON SUSTAINABLE ENERGY

bull [5] ndash Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoCoordination of Wind and Pumped-Storage Hydro Units for Managing Transmission Securityrdquo 2012

bull [6] Mohammad Shahidehpour Fellow IEEE and Mohammad Khodayar Member IEEE ldquoEnhancing the Dispatchability of Variable Wind Generation by Coordination With Pumped-Storage Hydro Units in Stochastic Power Systemsrdquo

bull [7] ldquohttpwwwhydroworldcomarticlesprintvolume-21issue-5articlespumped-storageconverting-to-variable-speed-at-a-pumped-storage-planthtmlrdquo